Subungual hematomahttps://en.wikipedia.org/wiki/Subungual_hematoma
Subungual hematoma is a collection of blood (hematoma) underneath a toenail or fingernail. It can be extremely painful for an injury of its size, although otherwise it is not a serious medical condition. Subungual hematoma can resolve on their own, without treatment. If they are acutely painful, they may be drained.

○ Diagnosis and Treatment
Observation is enough in most cases. If there is severe pain, a hole may be made to drain the blood. A nail with a hematoma is highly vulnerable to fungal infection.

  • Subungual hematoma of a toe
References Subungual Hematoma - Case reports 38111403 
NIH
The authors present the case of a 64-year-old male who presented to the emergency department due to foot trauma. He sustained a large subungual hematoma, which was drained. Following the procedure, the patient achieved complete resolution of his pain.